1. Field
Embodiments of the present invention relate to an electric brake system which has a simplified structure and allows precise pressure control.
2. Description of the Related Art
A brake system for braking of a vehicle is essentially mounted on a vehicle, and various systems have recently been proposed to obtain stronger and more stable braking force. Examples of brake systems include anti-lock brake systems (ABSs) to prevent slippage of wheels during braking, brake traction control systems (BTCSs) to prevent slippage of driving wheels during rapid acceleration from a stop or upon sudden acceleration of a vehicle, and vehicle dynamic control systems (VDCs) to stably maintain a driving state of vehicles by controlling a brake hydraulic pressure through a combination of an anti-lock brake system with a brake traction control system.
The electronic-controlled brake system includes a plurality of solenoid valves to control a brake oil pressure transmitted to a caliper brake (also called a hydraulic brake or a disc brake) mounted on a wheel of a vehicle, a pair of a low-pressure accumulator and a high-pressure accumulator to temporarily store oil flowing out of the wheel cylinder, a motor and a pump to forcibly pump the oil in the low-pressure accumulator, a plurality of check valves to prevent reverse flow of the oil, and an electronic control unit (ECU) to control the operations of the solenoid valves and the motor. These constituents are compactly installed in a hydraulic block formed of aluminum. In addition, once a driver pushes a brake pedal, a hydraulic-pressure supply device senses displacement of the pedal through a pedal displacement sensor, and receives an electric signal indicating the driver's braking intention from the pedal displacement sensor, such that pressure is supplied to the wheel cylinder.
A representative example of the electronic control brake system including the above-mentioned hydraulic-pressure supply device has been disclosed in United States Patent Publication No. US 2012/0091787. In this cited reference, the hydraulic-pressure supply device is configured to operate the motor in response to foot force applied to a brake pedal, such that brake pressure is generated. In this case, the brake pressure converts rotational force of the motor into rectilinear motion and presses a piston, resulting in the occurrence of brake pressure.
However, the above-mentioned electronic control brake system having a single-acting structure must control the piston pressurized either during regeneration of pressure or during boosting of the generated pressure to return to an original position in such a manner that the piston is re-operated at the original position, such that it is difficult to perform rapid pressure generation and precise control.
In addition, in order to electronically control the brake system as well as to perform various functions, a plurality of valves and flow passages are needed such that the entire system including such valves and flow passages becomes complicated in structure.